The group B streptococcus is a major pathogen for the newborn infant. These studies propose to examine immunological responses to group B streptococcal antigens in animals and in parturients and their newborn infants in an attempt to differentiate carriage from infection. Experimental infections (sepsis/meningitis) will be produced in the infant rat model in an attempt to expand our understanding of human neonatal disease. Tissue responses to infection and host immunological mechanisms will be examined. Results will be evaluated for their possible application to prevention and treatment of group B streptococcal infections.